Light duty tires (e.g. passenger vehicle tires and light duty truck tires, preferably passenger vehicle tires) may experience internal heat build up and a corresponding increase in operating temperature as the light duty tire is being used on an associated vehicle.
Such light duty tire internal heat buildup is considered herein to be significantly different from internal heat buildup generated under a relatively heavy load in heavy duty tires (e.g. heavy duty trucks and large off-the-road material hauling vehicles carrying heavy loads). Heat build up in a light duty tire tread during the working of such light duty tires can be of sufficient magnitude to cause such light duty tires to operate at significantly high temperatures, particularly at high speeds, and thereby have an impact upon their long term heat durability.
For this invention, it is proposed to provide at least one transition rubber layer of at least one silica-rich, cis 1,4-polyisoprene rubber based composition positioned between the light duty tire tread cap layer and underlying circumferential belt plies to promote low hysteresis to reduce heat generation and thereby promote an associated long term durability, to promote adhesion of the transition rubber layer and adjoining rubber layers and also to promote tear resistance of the transition rubber layer.
Further, by way of providing such transition rubber in a form of a silica-rich rubber composition, the transition rubber layer in the light duty tire may be of a color which contrasts with the black color of adjoining carbon black reinforced, diene-based elastomer based tire components when said transition layer contains only a minimal amount of carbon black reinforcement, if any, and contains a colorant.
In one aspect, the light duty tire of this invention is a tire having a maximum load bearing capacity of 3,500 pounds (1587 kg), preferably a maximum load bearing capacity of 3,000 pounds (1361 kg), and therefore is considered herein to be significantly different from a heavy duty tire having a minimum load bearing capacity of 4,000 pounds (1814 kg). Reference: The Tire And Rim Association Hand Book. 
The term “phr” where used herein means “parts per weight of a specified material per 100 parts by weight rubber, or elastomer, in a rubber composition”.